In mine work, such as salt or coal mining, or in underground construction, such as tunnels or other excavations, it is necessary to support the roof of the excavation to prevent cave-ins. Among the most common means presently in use for effecting such support are roof bolts, which are inserted into bore holes and hold a metal support plate against the roof surface.
Prior art reveals two types of roof bolt installations. In the first, the support plate is installed dome-side facing the floor and the flat-side against the roof surface. The installation suffers from a serious drawback. The roof surface is generally not horizontal, but has undulations in its surface. The support plate is therefore not flush against the roof, and provides less than optimal support. When the plate is not horizontal, stresses on the support plate and bolt are uneven, resulting a weaker support system, and possible failure of the plate or bolt. Also, in some mines the strata shift horizontally. When the surface of the roof in the vicinity of the plate is uneven, there is a greater chance that horizontal shifting will cause bolt failure by preventing movement of the bolt.
In the second, as shown in U.S. Pat. Nos. 8,052,353 and 7,708,087, the disclosures of which are hereby incorporated by reference, a concave surface is drilled into the roof and the domed-side of the support plate is inserted into the concave recess. This installation method provides less than optimal support. The dome in the support plate provides structural integrity to the support plate. However, when the dome is facing the roof, there is a greater chance that the vertical pressure on the support plate will crush the dome.
A roof bolt installation tool and installation method is needed which overcomes these deficiencies of the prior art.